This invention relates to methods for removing organic cations to very low levels from polar fluids.
Cationic organic compounds, particularly the onium compounds, are often highly toxic even when present in very dilute solutions. For example, quaternary ammonium and other onium salts have neuromuscular blocking properties which upon exposure cause muscular paralysis. This type of toxic effect is discussed in Introduction to Chemical Pharmacy, 2nd. ed., Wiley & Sons, 125 (1964).
The removal of organic cations from aqueous or other polar liquids, particularly to low levels needed to avoid unacceptable toxicity, is often a difficult problem. Methods for removing these organic cations, such as passing the solutions through a cation-exchange resin or extracting the cations from the solutions with a water-immiscible organic phase containing a phenolic compound as described in U.S. Pat. No. 4,487,698, are known. Unfortunately, both of these methods are either not effective in removing the organic cations to levels below 5 parts per million (ppm) or are impractical due to the required large volumes of solvents and the contamination of the aqueous or other polar phase with phenolic compounds. Such methods are usually totally ineffective when it is desired to remove an organic cation from a polar liquid containing other different cations which are desirable to retain in the polar liquid.
In view of the deficiencies of the conventional methods for removing organic cations from polar liquids, it is highly desirable to provide a method which is capable of removing essentially all of an organic cation from a polar liquid.